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March 9, 2007 -- Smelling a scent while learning and again during deep sleep may help you remember what you learned, German scientists report.
They studied 74 healthy adults who were 20-30 years old. Participants saw pairs of cards jumbled across a computer screen.
Some participants sat at computers in a room perfumed with rose scent. Others sat at computers in unscented rooms.
All participants spent the night at a sleep lab. They wore electrodes on their scalp to monitor their brain activity during sleep.
While participants slept deeply or while they experienced light REM (rapid eye movement) sleep, their rooms were briefly perfumed with the rose scent.
The next day, participants took a computerized pop quiz that challenged them to locate the card pairs they had seen the previous day.
Participants who had smelled the rose scent twice -- during the computer session the previous day and during deep sleep (non-REM sleep) -- performed best on the quiz.
Smelling the rose scent during light REM sleep didn't boost test scores.
For comparison, the researchers repeated the experiment with another group of people who only smelled the rose scent during the daytime. That didn't affect test scores.
To learn more about the scent-memory connection, the researchers asked 14 participants to sleep in a magnetic resonance imaging (MRI) scanner.
The scanner is a large device with a tunnel in the middle of it. Participants slept with their heads in the scanner. They had participated in past MRI studies, so they were familiar with the MRI machine and were able to fall asleep in the unusual setting. They also wore earplugs and headphones to reduce noise.
Their brain scans show that a certain brain area -- the hippocampus -- was particularly active while participants smelled the rose scent during deep sleep.
The hippocampus may be a key brain area in building memories, and scent may strengthen that process, the researchers conclude. They didn't test any other smells to see if rose scent is particularly memorable.